1. Field of the Invention
The present invention relates to motor vehicle wheel with a tire mounted on a wheel rim, whereby an insert exhibiting a ring-shaped, rotating, sound-absorbing material is placed inside the tire interior enclosed by the rim and the tire. The invention furthermore relates to a process for manufacturing a sound-absorbing insert.
2. Discussion of Background Information
It is known that the tire vibrations created while rolling a tire is one of the main causes of unpleasant radiating sound. The vibration load created inside the tire body is very large and therefore creates high sound levels. The sound waves originating in the tire body are partially deflected to the exterior via the tire side walls, and partially transferred via motor vehicle components into the vehicle interior. It is now known that the insert of sound-absorbing material in tires or within the interior space created between the tire and wheel rim reduces the radiating sound load.
A solution known from prior art that also relates to a vehicle wheel of the type mentioned at the outset, deals with achieving an effective reduction of the sound waves emanating from the tire body while suggesting a simple way for assembly and disassembly. To this end it is suggested to insert the sound-absorbing material in a flexible tube that can be mounted together with the tire due to its flexibility. The embodiment as a tube has the advantage of an easy assembly method. However, especially at higher speed, when the occurring centrifugal forces become relatively large, a lower weight would be desirably.
A vehicle air tire which is completely or partially covered on its interior surface with a sound reducing coating of open-cell foamed material is furthermore known from the German patent document DE 30 42 350 C2. In order to achieve an effective dampening of the body sound in the frequency ranges that are particularly physiologically significant, it is suggested to use a special, sound-reducing, cross-linked polyurethane foamed material applied at a certain coating thickness.
EP-0 038 920 A1 discloses the addition of vibration absorbers, preferably mounted securely to the tire interior with regard to tension and torque. These vibration absorbers can consist of rubber, synthetic material or similar and additionally contain dampening inserts. DE 29 46 273 A1 also suggests to place sound-absorbing material in the interior of a tire, whereby this document discloses an arrangement of the sound-absorbing material, consisting of open-cell foamed material, on the interior side opposite the tire profile. Among other things it is suggested to fill the whole tire interior with open-cell and roughly structured foamed material. For reasons concerning the firmness, a carrier skeleton can thereby also be embedded in the foamed material.
Open-cell foam material is generally particularly well suited to particularly effectively lower the very high air sound levels created during driving. As a result, the tire-/road sounds radiating to the exterior as well as the noise present in the vehicle interior are reduced. The expert knows that there exists a series of such foamed materials that are very good at meeting these requirements.
In addition there are different materials that act equivalently in absorbing sound in the tire interior, such as absorbent cotton, wool, or felt, finding use as fleece or other form.
In practice, however, changes in the sound-absorbing characteristics of the sound-absorbing materials suited for tire insertion occur, particularly at higher speeds, due to the influence of the increasing centrifugal force, increasing with increased travel velocity, whereby the extent of the changes are also dependent on the material. The sound-absorbing characteristics thereby change due to the deformations occurring in the material and as a result of cross sectional changes of the insert of this material.